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AIJSTPME (2013) 6(1): 11-17 Design and Development of Electronic Fuel Injection Control System Program for Single Cylinder Diesel Engine SittichompooS. Combustion Technology and Alternative Energy Centre-CTAE, College of Industrial Technology, KMUTNB, Bangkok, Thailand Theinnoi K. Combustion Technology and Alternative Energy Centre-CTAE, College of Industrial Technology, KMUTNB, Bangkok, Thailand Sawatmongkhon B. Combustion Technology and Alternative Energy Centre-CTAE, College of Industrial Technology, KMUTNB, Bangkok, Thailand Abstract This research aimed to evaluate mainly on engine-out emission of a single cylinder diesel engine on two conditions of fuel injection system: mechanically and electronically controlled fuel injection system. The research engine was modified to have changeable fuel injection system. The in-house built PECU was capable of producing 3 consecutive injection pulses. Fuel pressure was adjusted between 500 bar to 1100 bar. Engine with electronically controlled fuel injection system produced less NOx than original engine approximately 50%. However, as the result of higher injection pressure HC and CO were increased due to fuel impingement on combustion chamber. Keywords: Electronically controlled fuel injection system, Common Rail fuel injection system, Single cylinder diesel engine, Multiple injection 1 Introduction Diesel engines usage has been highly demand strategies have been developed to improve the engine compared to spark ignition engines in order to performance. Common Rail (CR) fuel injection simplicity, cost and performance [1]. Conventional system is one of electronically controlled fuel diesel engines generally employ the conventional injection system that has become the main feature for mechanically fuel controlled injection systems. The CI engine nowadays. The system is able to provide engine’s air to fuel ratio (A/F ratio) and fuel injection various and flexible control of injections [3,4] such timing are not precisely controlled under operating as injection event, injection pressure, injection rate conditions, therefore; desired engine performance, and injection number in a cycle of operation. break specific fuel consumption (BSFC), and Electronically controlled fuel injection system has emissions level (e.g. nitrogen oxide, particulate proven to be the major improvement of diesel engine matter) can hardly be achieved [2]. that is able to achieve reduction in both aspects of In additions, the growing concern regarding to the fuel consumption rate and engine-out emission [5]. global warming and the depletion of fossil fuel Operating noise from the engine is also reduced, due resource, the demand of diesel engine has gradually to the use of high pressurised fuel atomiser and increased due to the better fuel economy, higher sophisticated control of injections pattern. The trend durability and wider range of renewable fuel of diesel technology has been focused on increasing (e.g. biodiesel). The researches on fuel injection injection pressure and injection strategies, which 11 Sittichompoo S. et al. / AIJSTPME (2013) 6(1): 11-17 achieved the higher combustion efficiency and lower 2 Experimental procedure and apparatus emissions [5,6]. 2.1 Apparatus CR system has been employed for multi cylinder This experimental research was carried out on a diesel engine for passenger cars and trucks. Although YANMAR TF DI 90, four stroke single cylinder there is no single cylinder diesel engine with naturally aspiration diesel engine which is modified electronically controlled fuel injection system and equipped with conventional Common Rail fuel commercialised in the market. The major advantages injection system (Figure 1, 2 and 3). The CR control of CR system can be referred in terms of injection period and fuel pressure are controlled improvement in the thermal efficiency and fuel using in house microcontroller based software. economy compared to mechanism injection system Combustion chamber geometry was kept unchanged. diesel. Also, the lower fuel economy and the The engine specifications are given in table 1. A PC controlled emission in order to keep within the programmable electronic control unit was designed current limits and meet forthcoming scheduled to split fuel injection into multiple injections (i.e. pre- stringent emission standards (e.g. Euro 6, Tier 4, injection, main-injection, and post- injection) with Low Emission Vehicle III (LEV III)). Therefore, the adjustable fuel pressure up to 2000 bar. introduction CR system in single cylinder diesel engine should be an interesting method. However, Table 1: Experiment engine details. the high cost implement is the main disadvantage in this small system. Engine Before After There are several factors contributed in order to have specification Modification Modification a fully controlled in fuel injection such as fuel Model YANMAR TF-DI 90 injection pressure, injection timing, dwell time, and amount of fuel injected [7]. Fuel injection pressure is Number of 1 the main advantage of CR system as it can be cylinders controlled independently from engine speed [8] that Cylinder-head 2 valve, Over Head Valve results in designable injection pressure at any engine conditions. Sophisticated control of injection Combustion system Direct Injection-DI pressure in the rail is needed to optimise with the Bore/stroke 85 mm/87 mm variation of pressure drop between each injection event [9] which affects actual fuel amount injected. Displacement 3 Dwell time is a crucial parameter that has the very volume 493 cm impact on combustion process [5]. Previous studies Compression ratio 16.6:1 showed the various length of dwell time utilised between 0.5 – 1.8 ms [5, 7, 8, 10, 11]. The reduction Cont. Rating 5.9@ 2400rpm of dwell time is mainly development with fuel Output (kW) injector by having faster method of actuation. The Max. Output (kW) 6.6@ 2400rpm approaches to 0 µs of dwell time capable of Bosch Type Electronically producing close couple multiple injection or injection Mechanically controlled fuel trains [3] which enable more advance combustion. Injection system Fuel injection injection In this study, a preliminary work was to design and system system install electronically controlled fuel injection system Engine into single cylinder agriculture diesel engine. The Fuel pump mechanically Electrically experiment on engine performances and engine-out mounting driven driven emission were carried out for both conditions of engine before and after modification. Horiba MEXA-584L gas analysis included measurement of CO , CO by non-dispersive infrared 2 (NDIR), O2 by magnetopneumatic method, NOX by chemiluminescence detection (CLD) and total unburned hydrocarbons by flame ionisation detector (FID). H2 concentrations were measured by gas 12 SittichompooS. et al. / AIJSTPME (2013) 6(1): 11-17 chromatography. For all the conditions, engine out, injection system were performed at 3 different measurements of NOX, CO and HC were recorded. injection patterns are describe in table 2. To note that mode 0 represented standard injection with Electric motor High pressure conventional mechanically controlled fuel injection fuel pump system and mode 1 through mode 9 represented CR electronic fuel injection system. The combustion of conventional diesel fuel injection o Crank system with standard injection timing at 20 bTDC position P.E.C.U. Pressure and with CR injection system setup were examined sensor accumulator under a constant engine speed of 1500 rpm with an engine load of 75% of maximum engine load. Rail Table 2: Engine Test Injection Strategies Personal pressure Fuel Mode Inj. Pressure Inj. Pattern Computer sensor Injector (Bar) Pilot Main Post 0 200 Figure 1: CR system diagram for modified engine 1 500 2 500 3 500 4 800 5 800 6 800 7 1100 8 1100 9 1100 Figure 2: Fuel Injection Equipment Unit In the case of engine after modification which fuel pump was driven by external electric motor, external energy as pumping work must be taken in account using equation (1). Wpump was obtained during experiment as the product of positive area of voltage and current from electric motor. W1000 100% (1) t BSFCWHHV W 6 pump 3.610 Where = Thermal efficiency t Figure 3: CR injector mounted on modified cylinder W = Brake work from engine (kW) head BSFC = Brake Specific Fuel Consumption (g/kW.h) HHV = High Heating Value of fuel (MJ/kg) 2.2 Procedure The experimental were carried out on a engine test Wpump = Work required by fuel pump (W) rig equipped with external cooling system and an in- house built fuel consumption meter. Tests with 13 Sittichompoo S. et al. / AIJSTPME (2013) 6(1): 11-17 3 Results and discussion )e 70 ko 500 bar 800 bar 1100 bar 3.1 Fuel injector test /trs60 g 50 The experiment on fuel injector at various injection n (m patterns as shown in table 3 and injection pressure tio 40 intended to observe the in-house built control unit tra capability to manipulate both fuel injection pressure ne 30 cn in the pressure accumulator (rail) and injection event. co 20 Fuel amount injected was under validation with on 10 standard injector test bench Bosch model: H-S/EFEP tic jen 0 130. Fuel injection waveform and rail pressure were I recorded for further investigations. Injection Strategy Table 3: CR Injector Test Conditions Figure 4: CR Injector characteristics Inj. Duration (ms) Strategy Pilot Main Post Injection waveforms in figure 5 show the pattern of instantaneous fuel pressure drop of all injection 1 0 0.1 0 strategies at injection pressure of 800 bar. During 2 0 0.5 0 double injections and triple injections, pattern of 3 0 1 0 pressure drop were uniform. They occurred at the end of injection almost the same time at falling edge of 4 0.27 0.1 0 injection waveform. These instantaneous pressure 5 0.27 0.5 0 drop [9] were caused by the effect of fuel in pressure 6 0.27 1 0 accumulator (rail) begin to compensate the absence of pressure during the control piston moving down to 7 0.27 0.1 0.1 close injector needle. This simultaneously happens 8 0.27 0.5 0.2 when pressure balanced valve [3] is closing. The rail 9 0.27 1 0.3 pressure is rising again as the result of pressure balanced value fully closed as prove of the actual end Fuel injection rate from fuel injector has non- of injection. The result demonstrates the potential to linearity characteristic in the beginning of injection reduce dwell time between pilot- main injections and event as shown in figure 4. It should be noted that the main-post injection down to tens of microsecond (µs) amount of fuel injected under lowest excitation which leads to the potential for sophisticated duration (100µs) has no significant effect for all injection strategies. injection pressure conditions. As solenoid actuator 20 1200 requires certain amount of time to gain sufficient t) Single injection Double injection Triple injection lo 1000 ) electromagnetic force to lift the pressure balanced (V15 r valve in the injector [3]. However, the longer mr 800 (Ba fo er injection duration (500 µs) shown the linearity ev 10 600 ssu a re characteristic compared to the 100 µs injection n W Pilot injection Main injection Post Injection 400 l P duration to actually start the injection. The dwell time tio 5 ue of 1.8 ms was used for investigated fuel injection cje 200 F nI strategies during experiments. The higher injection 0 0 pressure and longer injecting duration resulted in 0 0.002 0.004 0.006 0.008 0.01 increasing fuel amount injected. It can be clear that Time(s) the linear change of fuel injection amount for Figure 5: Injection waveforms against rail pressure strategy 2 and 3 (Figure 4). at various injection strategies. It can be noticed that the rail pressure utilised in double consecutive injection mode was higher than other testing mode due to the overshooting with high 14
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